The subject technology is based on innovative functional ionic liquid hybrid materials. Ionic liquids (ILs) are a unique class of organic salts with negligible vapor pressure, nonflammability, good room-temperature ionic conductivity, wide electrochemical windows, and favorable chemical and thermal stability. They are ideal candidates for safer electrolytes in li-ion batteries.
Developments are being made in unique ILs and nanohybrid electrolyte solutions that are tailor-made or explicitly designed to complement a specific combination of electrode chemistries. While ionic liquids show great promise, their use as electrolytes for Li-ion batteries have been limited for three reasons: first, the fraction of the ionic conductivity of the electrolyte arising from mobile lithium ions (i.e. the lithium transference number) is typically low, making cells using IL electrolytes prone to polarization; second, most ILs exhibit only moderate total ionic conductivity at low temperatures, and third, conventional ionic liquids have been shown in the literature to be incompatible with graphite anodes, the predominant anode used in commercial Li-ion batteries. See, for example, US20120039824 and US20140154588.
The present invention provides for functionalized ionic liquids, and ionic liquid-based electrolyte combinations that allow for stability with graphite-based anodes in Li-ion batteries. This invention optimizes non-flammable electrolyte formulations based on ionic liquids, lithium salts, organic co-solvents, film forming additives/co-solvents, and nanoparticle additives that address problems associated with graphite instability, such as cationic co-intercalation, and poor surface electrolyte interphase (SEI) formation.
There is a need in the art to implement the inherently safe class of molecules known as ionic liquids in Li-ion batteries with graphite-based anodes.